Thank you so much for response!
3. Works perfect!
2. Just found out that on a real version of the website (not wp editor) everything is fine
1. I tried what you suggested, but I got a quite small image (the image was a different size than recommended 1930 by 600) at the left corner of the page as a result. I think I will just leave it as it was originally hoping for the new updates. I am using a ‘full screen image’ option. Ideally the banner would be auto-adjustable for mobile/tablet screens width. I use a portrait as a banner and it gets considerably cut from both sides, I guess because banner = background.
Curious to see new updates and thank you again so much for your wonderful support!
Maria